Dunlop is the study’s lead author from the Northwestern University Feinberg School of Medicine in Chicago.

“We know that being active is good for your health and we know a sedentary lifestyle is bad for your health,” she said. But few studies have examined whether moderate to vigorous physical activity offsets the possible negative effects of being sedentary.

Dunlop and her colleagues write in the Journal of Physical Activity and Health that Americans already lead sedentary lifestyles.

Among older Americans disability is also a major concern because it has been linked to increased medical spending and a higher risk of going into a nursing home or other care facility.

If future studies can confirm that sedentary behaviour causes disability, which this study does not, then older people may possibly avoid becoming disabled by being more active throughout the day.

For the new report, Dunlop and her colleagues analysed data collected in 2003 through 2006 as part of a long-term government study of American health.

The researchers used information on 2,286 adults who were 60 years old or older, had worn a device that measures physical activity for at least four days and had a physical exam.

Participants were considered to have a disability if they couldn’t perform a self-care task, such as getting dressed, by themselves.

Survey participants spent about 14 hours awake each day, on average. Of that, an average of nine hours was spent sitting or otherwise not moving.

After taking into account the amount of time people spent doing moderate to vigorous physical activity, their age, their health and whether they were well-off, the researchers found that each hour of daily sitting was linked to a 46 per cent increased risk of having a disability.

The study can’t say whether a sedentary lifestyle leads to disability or if having a disability leads to a sedentary lifestyle, however.

In addition, the authors note that their records of physical activity may not take into account some forms of exercise, because the devices that participants wore may not pick up upper body movement or cycling. Participants also didn’t wear the devices while swimming.

Stephen Kritchevsky told Reuters Health it’s too early to tell if interventions that get people moving during the day will prevent disability, but they couldn’t hurt because other studies suggest activity improves functioning.

He heads the Sticht Center on Ageing at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina and wasn’t involved in the new research.

“The fact that people are physically limited in some way is even a bigger reason to try and do things, because there is plenty of research that shows that’s likely to improve function,” Kritchevsky said.

Dunlop said older adults should be as physically active as possible. They should also know that being sedentary is possibly bad for their health.

“The goal here is to accumulate more light activities to replace the sitting and keep going on the moderate activity that you’re already engaged in,” she said. (Reuters Health)